configure: Use an explicit CONFIG_IVSHMEM rather than CONFIG_EVENTFD

Rather than relying on everywhere that cares about whether the host
supports ivshmem using CONFIG_EVENTFD, make configure set an explicit
CONFIG_IVSHMEM.

Signed-off-by: Kamil Rytarowski <n54@gmx.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1500021225-4118-3-git-send-email-peter.maydell@linaro.org
[PMM: split out from another patch, add commit message]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
3 files changed